1. Field of the Invention
The present invention relates to a reproducing apparatus of an optical recording medium for reproducing information from an optical recording medium such as an optical card.
2. Description of the Prior Art
For instance, as disclosed in Japanese laid open patent No. 60-69873, No. 61-48135 No. 61-50115, and the like, as a construction regarding the reproduction of an information signal from an optical card, there has been known a construction such that a laser beam is radiated onto track trains and a pit image corresponding to one track train is enlarged and formed onto a line sensor comprising, for instance, a CCD (Charge Coupled Device) in which a number of photo sensitive elements are arranged in a straight line. Information of one track train can be simultaneously reproduced by using the line sensor. The optical card is fed step by step at the rate of three or four steps to one track train. A signal is reproduced by scanning at each position.
On the other hand, in Japanese laid open patent No. 62-52730, there has been disclosed a construcion such that information recorded on an optical recording medium is reproduced by using an area image sensor in which a number of photo sensitive elements are arranged on a two-dimensional plane. That is, a system for reading out information on a unit basis of a block consisting of a set of track trains is disclosed in such literature.
The foregoing reproducing apparatus using the line sensor has a drawback such that it is difficult to reproduce at a high speed because of the loss due to the movement time of the optical card.
The high speed reproduction can be performed by the system using the area image sensor. However, according to the above literature, there is a problem such that the apparatus can be applied only to the card having the good linearity of the track trains such as a read only card which is formed from a mask by printing. That is, nothing is shown with respect to solutions in the case where the track trains and the detecting elements of the area image sensor are nonparallel because of a zigzag motion of the track trains due to mechanical vibration when recording by using a laser beam or due to a lack of compatibility among the apparatuses. To solve such a problem, there is considered a method of providing rectilinear guide grooves for guiding the recording beam so that parallel track trains are formed in order to prevent the zigzag motion of the track trains upon recording and to keep the parallel state between the scanning direction by the detecting elements of the area sensor and the track trains. However, since not only the memory capacity of a recording medium decreases but also it is meaningless to provide the guide grooves if they meander, rigorous technical management is needed to form the guide grooves.